石墨炉原子吸收分析中升温速率对基体效应影响的研究

本文系统研究Pb、Cd、Be在普通石墨管,热解涂层石墨管,全热解石墨管,石墨平台和钨钽热解石墨管和各种升温速率下的干扰。通过系统研究发现,钨钽石墨管结合使用快速升温(4000—6000K/s)对消除各种基体对Pb、Cd、Be干扰效果较好,可以避免使用基体改进剂,方法简便快速。     

石墨管涂覆-塞曼效应石墨炉原子吸收法测定土壤和沉积物中钡

样品使用硝酸-氢氟酸-高氯酸湿法消解,在0.015 mol·L-1硝酸介质中,采用自制涂钨石墨管,塞曼效应背景校正技术石墨炉原子吸收法测定了土壤和沉积物中的钡。经涂钨处理的石墨管表面形成了稳定的碳化钨层,有效避免了在原子化过程中待测元素钡与石墨管直接接触形成难熔碳化物,大幅度提高了检测的灵敏度和精密度,显著延长了石墨管使用寿命。碳化钨为间充型碳化物,在高温下可以产生较强的还原性氛围,可在一定程度上避免土壤和沉积物中常见的高浓度基体成分在原子化阶段生成难熔的氧化物而干扰钡的测定。氢氧化钙分子带背景干扰可以通过稀释法消除。该法测定土壤和沉积物中钡操作简便, 快速;检出限为4.2×10-10 g·g-1。环境样品中钡测定的相对标准偏差范围为2.0％～6.5％, 测定标准土壤的相对偏差均小于5％。     

钇基体改进剂石墨炉原子吸收法测定微量锗

本文利用硝酸钇做基体改进剂，石墨炉子原子吸收法测定植物样品及土壤样品中的微量锗，本方法采用涂钼热解石墨管，有效地避免了测定过程中锗的损失，方法的检出限为５．９×１０＾－１２ｇ，对于３０μｇ／Ｌ，锗的相对标准偏差为４．０％。     

原子吸收光谱法分析稀土元素的进展

本文从火焰、普通石墨管、热解涂层石墨管、钽带或钽舟、难熔金属碳化物石墨管、衬钽箔或片石墨管和钽平台－石墨管原子化器，综述了近几年来原子吸收光谱法分析稀土元素的进展。火焰原子吸收法测定稀土元素的灵敏度比大多数非稀土元素低；电热原子吸收法测定稀土元素的原子化温度、记忆效应和灵敏度和原子化器的组分关系极大，钽平台－石墨管试验效果最佳。     

钼盐涂覆—无火焰原子吸收法测定骨肿瘤患者血清中

用钼盐涂覆石墨管并以K2Cr2O7和Triton X-100为基体改进剂。GFAAS法测定骨肿瘤患者血清中微量铝，大幅度提高测定灵敏度和准确度。避免了沾污。特征浓度21.15pb/0.0044A·S。加标平均回收率104.92%，RSD＜8.17%。     

石墨管涂覆-塞曼效应原子吸收法测定生物样品中微量钡

以钨盐涂覆石墨管提高测定生物样品中钡的灵敏度，以基体改进剂提高分析精度，显著延长石墨管使用寿命，方法简便快速，得到了较好的回怍率和精密度。     

热解涂层石墨平台无火焰原子吸收法测定痕量锗

近年来用石墨炉原子吸收法测定微量Ge已有报导,但篇数不多。测定Ge的困难主要在1150℃的石墨炉内Na_2GeO_3被还原为Ge,高于1300℃时Ge被氧化为GeO,易挥发损失影响分析灵敏度。如何避免挥发损失,是人所关注的课题。Mino等人用NaOH作基体改进剂,在镀钽层石墨管中原子化,Burns和Dadgar用NaOH作基体改进剂,热解涂层石墨管直接测定有机锗化合物中Ge。国内以氨水、镍-草酸铵一氢氧化铵作基体改进剂,但均需采用萃取     

几种原子化器测钯的比较

本文较系统地比较了普通石墨管,热解涂层石墨管,石墨平台和钨石墨管测Pd以及测Pd时所受几种基体的干扰情况,发现钨石墨管抗酸干扰能力比其他几种管要强,抗其它干扰效果也较好。本文还比较了钨石墨管和钨钽石墨管,钨石墨管测Pd灵敏度高,且无记忆效应。     

石墨炉原子化器中原子化过程的研究——Ⅰ.石墨炉衬底材料对Al原子消失过程的影响

本文研究了在N_2和Ar气中,热解涂层石墨管、涂金属钨和锆层的热解石墨管中Al原子消失过程。实验表明,在热解涂层石墨管中,由于Al与N_2及石墨表面碳形成氰化物或氮化物,而在Ar气中形成碳化物的再蒸发,分解和原子化,使得Al原子蒸气的消失速度减慢。在涂难熔金属层的热解石墨管中不同程度上能防止上述化合物的形成,增加Al的峰吸光度值。     

用L''''vov石墨平台原子吸收光谱法测定红松种子中痕量钴和银

本文研究了在新焦化石墨管中装上L′vov石墨平台,原子吸收光谱法测定红松种子的痕量钴和银。分别采用L′vov石墨平台和普通石墨管,通过试验确定了干燥、灰化、原子化的温度和时间,并给出了石墨炉原子吸收光谱法测定痕量钴和银的条件。用L′vov石墨平台同普通石墨管的对比结果:测定Co的标准曲线,L′vov石墨平台法比普通石墨管法灵敏度高,线性范围宽,使用L′vov石墨平台时背景和基体效应降低了     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.